Spontaneous nanominiaturization of silicon microparticles with structural stability as flexible anodes for lithium ion batteries

Silicon (Si) is an ideal anode material for lithium ion batteries (LIBs) because of its high gravimetric capacity (3579 mAh g−1). However, Si anode undergoes sharp volume expansion during the charge/discharge process and then easily fragments to forfeit electronic contact, thereby forming dead Si, especially for micron-sized Si particles. We prepared a free-standing Si-based film anode, in which the micron Si particles are embedded by a coupled network of carbon nanotubes and the micro-nano structure is anchored by a carbon nanocoating layer. The networks can catch the nanominiaturized Si particles and provide continuous electrical contact during long cycling, thereby reviving the fragmented Si and maintaining lithium storage properties. This Si anode exhibits an ultra-high specific capacity of 3385.2 mAh g−1. The excellent cycling performance of 2345.3 mAh g−1 remained after 100 cycles at a current density of 0.3 A g−1. The pouch LIB based on the Si anode showed outstanding rate capacity and flexibility. This strategy is expected to solve the volume expansion and promote the application of the micron Si-based materials.